Tone modulating horn for loud speakers



Sept. 11, 1934. R R DU Y 1,973,200

TONE MODULATING HORN FOR LOUD SPEAKERS Filed Aug. 10. 1931 i 2i .2, W

Patented Sept. 11, 1934 H ,Y?" We i ell'firiES i rerii ti QrFEE TONE MODULATING HORN FOR LOUD SPEAKERS Richard R. Du Puy, St. Paul, Minn.

Application August 10, 1931, Serial No. 556,043

either upon a record of wax or similar material,

by means of a stylus or upon a film by means of light waves, as is practiced in the making of sound motion pictures, the low notes are accentuated and the high notes are somewhat attenulo ated. The average loud speaker at present in use has great variety of tone reproduction, high notes and low notes being reproduced with very little variation from the true tones transmitted to the loud speakers. Therefore, for ordinary tone reproduction without intermediate reccrding, the better grades of loud speakers at present in use are very satisfactory for true reprodua tion of sound. However, where there is an intermediate recording process, as above described, the loud speaker reproduces the accentuated low notes in their true recorded strength, thereby giving predominance to the low tones according to their predominance on the record. Where a horn of resonant material is used, these low notes set up a resonance in the walls of the horn itself which still further accentuates the low tones.

An object of the present invention is to make a loud speaker horn which will project sound waves from a loud speaker without distortion.

Such a device finds its principal field of usefulness in the sound motion picture industry at present, since where sound is reproduced with the low notes accentuated, these low notes cause a reverberation or drumming sound in theaters with imperfect acoustical properties and thereby reduces the intelligibility of speech and causes a distortion of music due to the preponderance of low notes. In order to attain the above set forth object, there is provided, in accordance with one feature of the invention, a horn having a small open inner end and a large open outer end, the small inner end being approximately the size of the diaphragm opening of a loud speaker to be used in conjunction with the horn. The inner surface of the horn is of a hard, smooth surfaced substance, such as ply-wood or other suitable material, which is backed on its outer surface by a nonresonant material, such as a semi-hard fiber board of the type used for sound deadening purposes.

These and other features of the invention will be more fully brought out in the following de- 1 Claim. (Cl. 181-27) scription and the accompanying drawing, wherein:

Figure 1 is a vertical, longitudinal section through a horn and loud speaker compartment made in accordance with the present invention, 0 the loud speaker being indicated in side elevation.

Figure 2 is a horizontal, longitudinal, sectional view through the device shown in Figure l, the loud speaker mechanism being shown in plan 55 View.

Figure 3 is a transverse, vertical sectional view of the loud speaker compartment just rear- Wardly of the loud speaker, and b Figure 4 is an enlarged view, similar to Figure 1, with the horn removed showing a horn mounting support secured to the loud speaker housing.

Referring to the drawing in detail, a loud H speaker housing compartment comprises a bottom member 1, top member 2, and side walls 8 and 4. These walls are secured exteriorly of a forward wall member 5 having a circular opening 6 therein of a size to receive the flange '7 of a loud speaker horn support member 8. A 0 secondary member of the forward wall comprises a member 9 having a circular opening 10 therein of approximately the size of the diaphragm opening in the forward end of the loud speaker.

A rear closure member 11 may also be provided. 5 The loud speaker enclosure shown may be of wood or other suitable material, although this compartment itself is not material to the invention and is merely shown as a convenient method of mounting the loud speaker in proper position with respect to the horn. A horn support comprises diverging top and bottom members 12 and 13, with side walls 14 and is of a size to receive the inner end of the horn 15. The horn 16 comprises top and bottom walls 17 and 18 and outwardly flaring side walls 19 and 20. The channeled sheet metal reinforcing member 21 is preferably mounted around the periphery of the large open end of the horn to secure the component parts of the side wall thereof together and to prevent injury to the marginal edges of the horn. The Wall structure of the horn which comprises the material feature of this invention, comprises a hard, smooth-surfaced inner wall member 22 which by itself would be resonant and an outer non-resonant member 23 secured in contact with the inner wall member 22 throughout its entire area. This structure prevents resonance of the horn material to the lower notes due to the larger and smaller vibrations Which has a tendency to dampen or diminish the lower tone frequencies, while the notes of higher frequencies are projected undiminished. This corrects the error produced by the recording of the sound Waves on a record and gives full tonal quality to the high notes and over-tones. The particular material of Which the inner, normally resonant lining member 22 is constructed, is immaterial so long as it has these qualities and those familiar with the art will find that a large number of materials will be found suitable for this liningmember. The. particular material used for the outer non-resonant sheating member 23 is also immaterial so long as it has the necessary non-resonant properties. Suitable substances for this purpose would include any semi-hard fiber board, cork-board, rubber, and a large number of equivalent substances.

I claim:

A loud speaker horn having the walls thereof constructed of a material having a thin hard, non-metallic, resonant inner layer, and a relatively thick, non-resonant sheathing secured thereto in close adjacent relation throughout, to dampen notes of low frequencies and to project unaltered notes of normal frequencies.

RICHARD R. DU PUY. 

